Grant Abrasive Sponge Grading Scale

[RustE]

Does anyone know if the FEPA grading scale was used for the Granat Abrasive Sponge?  These are the only Granat products that do not have the letter "P" before the grade number.

More specifically, are the two products below equivalent?  Where I could use one on the orbital sander and the other by hand to touch-up difficult areas.
Item No. 201769 - Granat Abrasive Sponge 115x140x5 MD 280 GR/20
Item No. 497204 - Granat Abrasive STF 80x133 P280 GR/100

 

[RustE]

[member=57769]TylerC[/member]  [member=101]Festool USA[/member]
Can you help with these questions?

 

[Administrator_JSVN]

We're still trying to confirm an answer on the FEPA question.

As to the equivalence question, the substrates of these two products are quite different.  This affects how the abrasive acts.  The abrasive for the sponge is not going to produce the same effect as the paper.

It is a challenge when shifting between abrasive types to have a perfect match or pick up where one type leaves off.  Different grit types, backing materials, coatings, etc. make it a challenge even within a range like Granat.

To break down the concept a bit., imagine each grit as a piece of sand.  And each grain of the sand is the same size (in this case 280).  Take a piece of that sand and put it on your desk.  This would represent a stiff backer like a heavyweight paper or cloth used in sheet abrasives.  Now imagine that same piece of sand on a kitchen sponge.  Same grit size, but totally different in how it would scratch a surface.  You won’t have the depth.  This is a very simplified approach.  Once you add more grits of sand and regulate their spacing, coatings, backings, etc., it becomes even more dizzying.

The 201769 is a MD or ‘medium’ grit in that range of abrasive types, and it is the coarsest of the sponges of that style (115 x 140 size).  The user may have to use 500 or 800 of that series to match the effect of the P280 of the 497204.

Also, what they are sanding will have an impact on how the abrasive reacts.

(Tyler & Rick)

 

[RustE]

What I want to accomplish is sanding between coats of water-based finishes on hardwoods.  I would like to use the RTS400REQ for as much of the surface area as possible, then use a hand abrasive for the difficult spots.

My initial thought was a one-to-one match for the grade of abrasive.  From what I read above, this might not be the best approach.

Would I do better using a different product by hand?  Maybe in conjunction with P240 on the RTS 400 REQ?

 

[Michael Kellough]

In my experience hand sanding with X grit produces a much rougher surface than machine sanding with the same grit.

 

[tjbnwi]

I use 240 on the RTS or ETS and 320 by hand for between coats finish sanding. I use only water bournes.

Tom

 

[RustE]

tjbnwi:  Thanks. That’s the kind of info that I’m trying to collect. Did you get to the solution through a few trials? Overall, are you happy with the results you’re getting?

 

[RustE]

[member=101]Festool USA[/member] :  You guys ever get more information about this topic?

I am thinking about using the suggestion made by [member=4105]tjbnwi[/member] with P240 on the RTS400 and P320 by hand.

 

[tjbnwi]

tjbnwi:  Thanks. That’s the kind of info that I’m trying to collect. Did you get to the solution through a few trials? Overall, are you happy with the results you’re getting?

It's a process I figured out years ago--about 45 of them....

Results are excellent.

Tom